The present invention relates to the recirculation of exhaust gas from the combustion cycle and the cooling of the recycled gas before it is returned to the combustion cycle of an internal combustion engine through the carburetor thereof.
Since the early 1970's, the automobile manufacturers have been required to reduce the emissions and/or pollutants resulting from the combustion cycle of an internal combustion engine. Various components have been added to the engine to control emissions including positive crankcase ventilation, exhaust gas recirculation, an evaporation control system and a catalytic converter in the exhaust line.
The emissions from the exhaust gases of automobile engines have been blamed for conditions such as smog occurring primarily in large cities, and one such emission of great concern are the oxides of nitrogen. An exhaust gas recirculation cycle has been used to reduce these oxides as the formation of nitrogen oxides takes place at the peak temperature period of the combustion process, and a temperature reduction can be accomplished by introducing small amounts of an inert gas into the combustion process. As the end products of combustion provide a continuous supply of relatively inert gas, the recirculation of the exhaust gases in the correct proportions to the engine carburetor accomplished the desired emission reduction.
As the exhaust gases from the exhaust manifold of an internal combustion engine are at a very high temperature level, a heat exchanger may be inserted in the recirculation passage to cool the exhaust gases returning to the combustion cycle. However, in view of the crowded condition of the internal combustion engine and related equipment in the engine compartment of an automotive vehicle, the insertion of a heat exchanger of sufficient size to provide the necessary cooling capacity for the exhaust gases becomes extremely difficult in view of the alignment of fittings, etc. The present invention provides a solution to the problem of providing sufficient space for the heat exchanger.
The present invention comprehends the provision of a compact heat exchanger in combination with an exhaust gas recirculation control valve where the unit is adapted to be connected to the intake manifold of the engine so that the cooled exhaust gases directly enter the intake manifold for mixing with ambient air and gasoline vapor proceeding through the carburetor to the combustion chambers of the engine. The exhaust gases exit from the exhaust manifold through generally internal passages to reach the heat exchanger.
The present invention also comprehends the provision of a compact heat exchanger in combination with an exhaust gas recirculation control valve in an integral housing whereby the passageway from the heat exchanger to the intake manifold is controlled by the exhaust gas recirculation valve. The control valve housing is mounted on a valve body containing the gas inlet and outlet passages leading to a heat exchanger laterally removed from the valve housing. This combination eliminates all need for external exhaust gas piping and potential sources of leakage at external connections.
The present invention further comprehends the provision of a compact heat exchanger combined with an exhaust gas recirculation control valve wherein the heat exchanger includes a plurality of U-shaped tubes through which the hot exhaust gases pass housed in a shell having cooling water inlet and outlet connections that communicate with the coolant from the engine cooling system.
Another object of the present invention is the provision of a combined exhaust gas recirculation control valve and a heat exchanger whereby the control valve and heat exchanger can be easily tested and calibrated prior to assembly to the vehicle engine.
Further objects are to provide a construction of maximum simplicity, efficiency, economy and ease of assembly and operation, and such other objects, advantages and capabilities as will later more fully appear and are inherently possessed thereby.